JP5674859B2 - A numerical controller with a function to estimate the life of the bearing that supports the spindle - Google Patents

Description

  The present invention relates to a numerical control device having a function of estimating the life of a bearing that supports a spindle of a machine tool.

  Bearings used as bearings for machine tool spindles gradually deteriorate due to friction and load, so it is necessary to replace them at an appropriate time. Conventionally, the total number of rotations and the total rotation time obtained by integrating the rotation speed and rotation time of the main shaft are used as a guideline for replacing the main shaft bearing in the machine tool. For example, Patent Document 1 discloses a numerical control device with a life management function, and the numerical control device includes an accumulated value of operation amounts related to the life of components of the movable part, and a preset life value of the movable part. And a display means for displaying the accumulated value with the content of determining the life of the component. Patent Document 2 discloses a method for monitoring the life of a bearing. This monitoring method calculates the number of rotations of the rotating body that supports the bearing and the average value of the load applied to the rotating body from the operating state of the machine. Then, obtain the bearing life value. When the integrated value of the rotation time of the rotating body exceeds the life value, a maintenance time message is displayed.

JP-A-5-208343 JP 2011-247660 A

  The life of the bearing that supports the spindle of the machine tool is affected by the force acting on the spindle. While the main shaft and the workpiece are not in contact with each other during non-cutting, the main shaft and the workpiece are in contact with each other during cutting, so that a force equivalent to the reaction force from the workpiece acts on the main shaft. Therefore, when cutting, the load on the bearing is larger than when not cutting, and the life is relatively shortened.

  Conventionally, however, no distinction is made between non-cutting and cutting, and the rotation speed and rotation time of the spindle are simply integrated, so the influence of the load on the spindle has not been considered. For example, the life management technique disclosed in Patent Document 1 merely adds up the amount of movement of the spindle, and does not consider the influence of the force acting on the components of the movable part. For this reason, when the predetermined cumulative value is reached regardless of the magnitude of the force applied to the member, it is determined that the replacement time is reached.

  Therefore, an object of the present invention is to monitor a cutting signal indicating a cutting state, and during non-cutting, the rotation speed and rotation time of the main spindle are integrated as before, and during cutting, the rotation speed and rotation time act on the main spindle. By multiplying the weight according to the force and integrating, and considering the influence of the load acting on the spindle during cutting in the integrated value, the life of the bearing that supports the spindle can be estimated more accurately. It is to provide a numerical control device having an estimation function.

The invention according to claim 1 of the present application is a numerical control device for controlling a machine tool having a function of estimating a life of a bearing that supports a spindle of a machine tool, wherein the rotational speed of the spindle and the torque of a feed shaft are driven. A control unit that controls the shaft, or a physical data acquisition unit that acquires at predetermined intervals from a detector attached to each drive shaft, and a cutting signal monitor that monitors a cutting signal indicating a cutting state output by the control unit , A load calculation unit for calculating a force acting on the main spindle from the torque of the feed shaft acquired by the physical data acquisition unit, and a weight corresponding to the force acting on the main shaft calculated by the load calculation unit. A weight extraction unit that extracts from a table, and when the cutting signal is in a non-cutting state, the rotation speed of the spindle is integrated every predetermined period, and when the cutting signal is in a cutting state, the physical data acquisition unit A first integration section for integrating the obtained rotational speed of the second spindle multiplied by the weight extracted by the weight extraction unit to the rotational speed of the spindle in a predetermined cycle, the integrated value obtained by integrating by the first accumulation unit A numerical value control device that estimates the life of the bearing based on the integrated value.
According to a second aspect of the present invention, there is provided a numerical control apparatus for controlling a machine tool having a function of estimating a life of a bearing that supports a main shaft of a machine tool, wherein the rotational speed of the main shaft and the torque of the feed shaft are determined using a drive shaft. A control unit to control, or a physical data acquisition unit that acquires at predetermined intervals from a detector attached to each drive shaft, and a cutting signal monitoring unit that monitors a cutting signal indicating a cutting state output by the control unit; A load calculation unit that calculates a force acting on the main shaft from the torque of the feed shaft acquired by the physical data acquisition unit, and a weight that is given in advance according to the force that acts on the main shaft calculated by the load calculation unit. a weight extraction unit which extracts, in the rotation signal monitoring unit the main shaft to monitor the rotational state signal indicating whether or stopped rotating, the pre-Symbol rotation state signal rotation, and, when the cutting signal is in a non-cutting state ,Previous When a predetermined period is integrated, and when the rotation state signal is rotating and the cutting signal is a cutting state, a second predetermined period obtained by multiplying the predetermined period by the weight extracted by the weight extraction unit is A second integrating unit that integrates every predetermined period; and a storage unit that stores the integrated value integrated by the second integrating unit, wherein the life of the bearing is estimated based on the integrated value. It is a numerical control device.

According to a third aspect of the present invention, the load calculating unit is an acceleration obtained by multiplying the acceleration of the feed shaft acquired by the control unit or the detector by inertia from the torque of the feed shaft acquired by the physical data acquiring unit. The numerical controller according to claim 1, wherein a force acting on the main shaft is calculated from a torque obtained by subtracting a minute torque.
The invention according to claim 4 is characterized in that the load calculating unit calculates a force acting on the main shaft from a torque obtained by subtracting a torque corresponding to the friction of the feed shaft from the torque of the feed shaft. It is a numerical control apparatus as described in any one of -3.

  According to the present invention, the cutting signal indicating the cutting state is monitored. When not cutting, the rotation speed and rotation time of the main spindle are integrated as usual, and at the time of cutting, the rotation speed and the rotation time correspond to the force acting on the main spindle. A function that estimates the life of the bearing that supports the spindle, which can be estimated with a weight and integrated, taking into account the influence of the load acting on the spindle at the time of cutting in the integrated value, and more accurately estimating the replacement time. A numerical control device can be provided.

It is a block diagram explaining the numerical control apparatus of this invention. It is a figure explaining the resultant force which acts on the main axis | shaft in the machine structure where each axis | shaft is three axes | shafts of X, Y, and Z orthogonal to each other, and a main axis | shaft moves to a Z-axis direction. It is a figure explaining the difference in the index value which judges the lifetime of a bearing depending on whether the weight which acts on a main shaft is considered. It is a flowchart explaining the process which calculates the index value which judges the lifetime of a bearing.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The present invention does not calculate the life value of the bearing that supports the spindle of the machine tool, but calculates an index value to be compared with the life value. The index value is not calculated simply by integrating the rotation time of the main shaft supported by the bearing, but is calculated taking into consideration the influence of the force acting on the main shaft. As a result, even if the life value is a fixed value, the influence of the force acting on the main shaft is taken into consideration, so that it is possible to accurately determine the life of the bearing. In the present specification, the index value, the integrated value, and the rotation time will be described using the same symbol M.

<Embodiment 1>
FIG. 1 is a block diagram illustrating a numerical control apparatus according to the present invention. In the numerical control device 20, each axis of the machine tool is driven and controlled by a servo motor 11 provided in a mechanical part of the machine tool 10. The life of a bearing that supports the spindle of a machine tool is affected by accumulation of wear, metal fatigue, etc., so the index values used to determine the replacement time are the rotation speed and rotation time of the spindle that the bearing supports. The cumulative value of is valid. However, since the life of the bearing is affected by the force acting on the main shaft, it is not sufficient as an index value to simply integrate the rotation speed and rotation time of the main shaft.

  For example, when the main shaft supported by the bearing is driven, the life of the bearing varies depending on the magnitude of the force (the magnitude of the current) acting on the main shaft even at the same total rotational speed. When the force applied to the main shaft is large, the force applied to the bearing also increases, so the life is inevitably shortened, and when the force applied to the bearing is small, the life is extended.

  Therefore, in the first embodiment, a cutting signal indicating a cutting state is monitored, and when the main shaft is in a cutting state for processing a workpiece, a weight corresponding to the force acting on the main shaft is applied to the rotation speed and the rotation time of the main shaft. Multiply and multiply. On the other hand, when the cutting signal is a non-cutting state that is not a machining state, the weights are integrated without multiplication. As a result, during cutting when the spindle and workpiece are in contact, the influence of the force acting on the spindle can be taken into account in the index value, so that the replacement time can be estimated with higher accuracy than in the case of simple integration. .

  Specifically, in the physical data acquisition unit 22 of the numerical controller 20, the rotation speed V (kΔt) of the main shaft and the torque S (kΔt) (k = 0, 1, 2, 3,. It is acquired every predetermined period Δt from the control unit 21 that controls each drive shaft (motor) of the machine 10 or a detector (not shown) attached to the drive shaft. Then, the load calculation unit 23 calculates the force D (kΔt) acting on the main shaft from the torque S (kΔt) of the feed shaft acquired by the physical data acquisition unit.

  FIG. 2 illustrates a mechanical configuration in which each axis is three axes of X, Y, and Z orthogonal to each other and the main axis moves in the Z-axis direction. The workpiece 33 placed on the table 34 is processed by a tool 32 attached to the spindle 30. When the Z-axis position is fixed and the X-axis torque is Sx (kΔt) and the Y-axis torque is Sy (kΔt), the force applied to the main axis is expressed by the X and Y axes as shown in Equation (1). The resultant force is D (kΔt). The resultant force D (kΔt) is a force acting perpendicularly to the main shaft, but here the resultant force is “D (kΔt) ≈force acting on the bearing”. The force acting on the bearing 31 may be obtained based on the configuration of the main shaft and the force D (kΔt) acting on the main shaft.

Next, in the weight extraction unit 25, a weight E (kΔt) that is multiplied by the spindle rotational speed V (kΔt) based on the value D (kΔt) calculated by the load calculation unit 23 is given as a force D _k given in advance. And a weight E (D _k ) correspondence table. The weight E (D _k ) is obtained from an actual measurement value or a simulation result.

For example, let L _k be the lifetime when the spindle is continuously driven at a predetermined speed V _k in a non-cutting state where the spindle and workpiece are not in contact. Then, in a cutting state in which the feed shaft controls the relative position between the main shaft and the workpiece and applies a force D _k to the main shaft, the life when the drive shaft continues to be driven at a predetermined speed V _k is expressed as L (D _k ), The lifetime at the time of cutting is L (D _k ) / L _k times that at the time of non-cutting. Therefore, as the weight E (D _k ) multiplied by the rotation speed V (kΔt) of the spindle, a value L (D _k ) / L _k obtained by dividing the life at the time of cutting by the life at the time of non-cutting can be considered.

  Next, the cutting flag monitoring unit 24 monitors whether the spindle is in a cutting state or a non-cutting state based on a cutting / non-cutting signal (flag) obtained from the control unit 21. The cutting signal is generated as a cutting state when a cutting feed code such as G01 and G03 on the NC program of the machine tool or a load on the spindle exceeds a predetermined value.

  When in the cutting state, the weight E (D (kΔt)) extracted by the weight extraction unit 25 is multiplied by the rotation speed V (kΔt) in the integration unit 26, and the second rotation speed as shown in Equation 2 is obtained. Calculated as V ′ (kΔt). Then, as shown in Formula 3, the absolute value of a value obtained by multiplying the second rotation speed V ′ (kΔt) in consideration of the weight by a predetermined period Δt is integrated in the integrating unit 26, and the index value M is calculated. . On the other hand, since the force does not act directly on the main spindle when not cutting, the absolute value of the value obtained by multiplying the rotational speed V (kΔt) by a predetermined period Δt as shown in Equation 4 is integrated as it is, The index value is M.

FIG. 3 shows (a) the weight E (D _k ) corresponding to the force D _k acting on the main shaft, (b) the main shaft rotation speed V (kΔt), and (c) the main shaft rotation speed V (kΔt). A value V ′ (kΔt) multiplied by a weight E (D (kΔt)) and its integrated value (index value) M ′ are shown. The integrated value (index value) M simply integrates the rotation speed V (kΔt) of the spindle. It becomes the value. Here, the predetermined period Δt is 1. Thus, it can be seen that the index value M varies depending on whether or not the weight is taken into consideration.

  The index value M calculated in this way is stored in the storage unit 27 and used for maintenance. For example, the index value M is output to an output unit (not shown) such as a display, and the operator determines whether it is time for replacement based on the result. Also, the index value is compared with a predetermined standard for replacement time, and if the index value exceeds, a warning is given that the replacement time is approaching, or the machine is stopped. In addition, while comparing the index value and the guideline for replacement, if the bearing life is approaching or if you want to use the bearing for a long time, the operation condition is automatically relaxed.

<Embodiment 2>
In the second embodiment, the rotation time M of the main spindle (the integrated value of the predetermined period Δt) (Note: Since the rotation time is an example of the integrated value, M representing the integrated value is used) is calculated. A rotation signal monitoring unit (not shown) acquires a rotation state signal (flag) from the control unit 21 and monitors whether the spindle is rotating or stopped. For example, when the S command, which is the rotation command of the spindle, is a value other than 0 on the NC program, it is regarded as rotating, and when it is 0, it is regarded as stopped.

  Then, when the rotation state signal is rotating and the cutting signal is a non-cutting state, the integration unit 26 calculates a rotation time M by integrating a predetermined period Δt as shown in Equation 5. On the other hand, when the rotation state signal is rotating and the cutting signal is the cutting state, the predetermined period Δt is multiplied by the weight E (D (kΔt)) extracted by the weight extraction unit 25 as shown in Equation 6. The rotation time M is calculated by integrating the second predetermined period Δt ′.

Here, the process for obtaining the index value (integrated value) M executed by the numerical controller 20 shown in FIG. 1 will be described with reference to FIG. FIG. 4 is a flowchart for explaining processing for calculating an index value for judging the life of the bearing. Hereinafter, it demonstrates according to each step.
[Step SA01] k and M are set to initial values (= 0).
[Step SA02] The rotational speed V (kΔt) of the main shaft supported by the bearing and the torque S (kΔt) of the feed shaft are acquired.
[Step SA03] The force D (kΔt) acting on the main shaft is calculated from the torque S (kΔt) of the feed shaft.
[Step SA04] The weight E (D (kΔt)) corresponding to the force D (kΔt) acting on the main shaft is calculated.
[Step SA05] It is determined whether or not it is during cutting. When cutting (YES), the process proceeds to Step SA07. When it is not during cutting (NO), the process proceeds to Step SA06.
[Step SA06] The rotational speed V (kΔt) is integrated with the index value (integrated value) M, and the process proceeds to Step SA09.
[Step SA07] The rotation speed V (kΔt) of the spindle is multiplied by the weight E (D (kΔt)) to calculate a second rotation speed V ′ (kΔt).
[Step SA08] The second rotational speed V ′ (kΔt) is integrated with the index value (integrated value) M.
[Step SA09] The integrated value M is stored in the storage unit.
[Step SA10] After a predetermined period Δt has elapsed, a value obtained by adding 1 to k is newly set as k, and the process returns to step SA02.

  A supplementary explanation of the flowchart described above will be given. The correspondence between the processing of each step of the flowchart and each unit of the numerical control device 20 of FIG. 1 will be described. The processing of step SA02 is the physical data acquisition unit 22, the processing of step SA03 is the load calculation unit 23, and the processing of step SA04 is the weight. The extraction unit 25, step SA05 corresponds to the cutting flag monitoring unit 24, steps SA06 to SA08 correspond to the integration unit 26, and the storage unit of step SA09 corresponds to the storage unit 27.

<Embodiments 3 and 4>
The feed shaft torque S (kΔt) includes the torque A (kΔt) associated with acceleration / deceleration of the feed shaft and the torque F (kΔt) associated with friction, so only the torque S ′ (kΔt) applied to the main shaft is extracted. For this purpose, it is necessary to subtract the torque A (kΔt) for acceleration / deceleration and the torque F (kΔt) for friction from S (kΔt) as shown in Equation 7.

  The torque for acceleration / deceleration is obtained by multiplying the inertia J applied to the motor driving the feed shaft by the detector attached to each drive shaft and the acceleration a (kΔt) obtained from the control unit. The acceleration a (kΔt) may be obtained by differentiating the position and speed. Further, the frictional torque F (kΔt) is calculated from static friction and dynamic friction when the motor is driven.

10 Machine tools 11 Servo motors

DESCRIPTION OF SYMBOLS 20 Numerical control apparatus 21 Control part 22 Physical data acquisition part 23 Load calculation part 24 Cutting flag monitoring part 25 Weight extraction part 26 Accumulation part 27 Storage part

30 Spindle 31 Bearing 32 Tool 33 Work 34 Table

Claims (4)

In a numerical control device for controlling a machine tool having a function of estimating the life of a bearing that supports a spindle of a machine tool,
A rotation speed of the main shaft and torque of the feed shaft, a control unit that controls the drive shaft, or a physical data acquisition unit that acquires a predetermined period from a detector attached to each drive shaft;
A cutting signal monitoring unit for monitoring a cutting signal indicating a cutting state output by the control unit;
A load calculation unit for calculating a force acting on the main shaft from the torque of the feed shaft acquired by the physical data acquisition unit;
A weight extraction unit that extracts a weight according to the force acting on the spindle calculated by the load calculation unit from a table given in advance;
When the cutting signal is in a non-cutting state, the rotational speed of the spindle is integrated every predetermined period,
When the cutting signal is in a cutting state, the rotation speed of the second spindle obtained by multiplying the rotation speed of the spindle acquired by the physical data acquisition unit by the weight extracted by the weight extraction unit is integrated every predetermined period. A first integrating unit;
A storage unit for storing the integrated value integrated by the first integrating unit;
With
A numerical controller that estimates the life of the bearing based on the integrated value. In a numerical control device for controlling a machine tool having a function of estimating the life of a bearing that supports a spindle of a machine tool,
A rotation speed of the main shaft and torque of the feed shaft, a control unit that controls the drive shaft, or a physical data acquisition unit that acquires a predetermined period from a detector attached to each drive shaft;
A cutting signal monitoring unit for monitoring a cutting signal indicating a cutting state output by the control unit;
A load calculation unit for calculating a force acting on the main shaft from the torque of the feed shaft acquired by the physical data acquisition unit;
A weight extraction unit that extracts a weight according to the force acting on the spindle calculated by the load calculation unit from a table given in advance;
A rotation signal monitoring unit the main shaft to monitor the rotational state signal indicating whether or stopped rotating,
Before SL during rotation state signal is rotated, and, when the cutting signal is non-cutting state, and integrating the predetermined period, in the rotation state signal is rotated, and, when the cutting signal is cutting state, the predetermined A second integration unit that integrates a second predetermined period obtained by multiplying the period extracted by the weight extracted by the weight extraction unit for each predetermined period ;
A storage unit for storing the integrated value integrated by the second integrating unit;
With
A numerical controller that estimates the life of the bearing based on the integrated value.   From the torque obtained by subtracting the torque corresponding to the acceleration obtained by multiplying the acceleration of the feed axis acquired by the control unit or the detector from the torque of the feed axis acquired by the physical data acquisition unit. The numerical control device according to claim 1, wherein a force acting on the main shaft is calculated.   The load calculation unit calculates a force acting on the main shaft from a torque obtained by subtracting a torque corresponding to the friction of the feed shaft from the torque of the feed shaft. The numerical controller described.